[dsymutil] Fix missing member initializer.

This bug was found by the MSan bootstrap bot:
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/5330/steps/check-llvm%20msan/logs/stdio

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224481 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed